Interpretive Summary: The use of alfalfa in grasslands can enhance the quality and quantity of forage produced we need to know more about how different types of alfalfa respond to clipping in a grassland. A project was initiated at the Northern Great Plains Research Laboratory in Mandan, North Dakota to evaluate the responses of a hay-type and two grazing-type alfalfas to clipping at different growth stages. Including alfalfa increased total yield from 38 to 185% without decreasing grass yield. The entry SCMF 3713, which has been released as AC Yellowhead, produced the most biomass and it and the hay-type alfalfa, Vernal, produced the most biomass when clipping was delayed until at least the flowering stage. Incorporating alfalfa into grasslands can enhance productivity without reducing grass yield and SCMF 3713 appears to be a good choice for this purpose.

Technical Abstract:
Incorporating alfalfa into rangelands can enhance the quantity and quality of forage production. We evaluated the impact of defoliation timing and selective defoliation on two grazing- (Anik and SCMF 3713) and one hay-type alfalfas (Vernal) near Mandan, North Dakota, USA. Entries were space-planted into an existing mixed grass prairie and clipped at either the mid-bud, flower or flower and subsequent vegetative stages. For each clipping treatment, half of the plots had only the alfalfa clipped and half had both the alfalfa and the associated native vegetation clipped. Plots without alfalfa were also included to evaluate the impact of alfalfa on grass and forb biomass. Including SCMF 3713 increased total productivity by 38 to 185% without lowering the productivity of the grass or forb biomass components. Plots with SCMF 3713 produced 17 to 26% more total biomass than the next highest entry every year. In 2003 and 2005, alfalfa biomass was increased 1.5 to 2.7 times by clipping only alfalfa in the flower and regrowth stage compared to a mid-bud clipping of only alfalfa. Vernal and SCMF 3713 generally produced more total biomass when clipping was deferred to the flower stage but clipping Anik in the mid-bud stage produced as much or more total biomass than did the later clipping treatments. Selective clipping of the alfalfa did not impact productivity. SCMF 3713 appeared to be a good choice for incorporating into rangelands. Producers with SCMF 3713 or Vernal should consider delaying defoliation until flowering to maximize productivity.